Multiplex communication system utilizing successive, different pulse modulation techniques



M. J. E. G'oLAY 2,567,203 MULTIPLEX COMMUNICATION SYSTEM UTIEIZINC SUCCESSIVE,

sept. 11, 1951 DIFFERENT PULSE MODULATION TECHNIQUES Original Filed Feb. 5. 1946 8 Sheets-Sheet l I BY 25M A747517; ey

Sept. 1l, 1951 M. J. E. GOLAY 2,567,203

MULTIPLEX COMMUNICATION SYSTEM UTILIZING SUCCESSIVE,

DIFFERENT PULSE MODULATION TECHNIQUES Original Filed Feb. 5. 1946 8 Sheets-Sheet 2 INVENTOR MARCEL EGOLAY BY 7M M700? ernfy nNOwN Wim@ f owN lll Ill m m .|.Illll N .GE

Sept. 11, 1951 A M. .1. E. GOLAY 2,567,203

MULTIPLEX COMMUNICATION SYSTEM UTILIZING SUCCESSIVE,

DIFFERENT PULSE MODULATION TECHNIQUES Original Filed Feb. 5. 1946 8 Sheets--SheerI 3 INVENTOR.

- MARCEL .1.5. GoLAY 2,567,203 zING SUCCESSIVE,

QUES

Sept. 11, 1951 M. J. E. GoLAY MULTIPLEX COMMUNICATION SYSTEM UTILI DIFFERENT PUL Original Filed Feb. 5. 1946 SE MODULATION TECHNI y 8 Sheets-Sheet 4 2,567,203 G sUCgEssIvE,

M. J. E. GOLAY EX COMMUNICATION SYSTEM UTILIZIN Sept. 11, 1951 MULTIPL Original Filed Feb. 5. 1946 DIFFERENT PULSE MODULATION TECHNIQUE 8 Sheds-Sheet 5 nOmN Sept. 11, 1951 M. J. E. GOLAY 2,567,203

MULTIPLEX COMMUNICATION SYSTEM TILIZING SUCCESSIVE,

DIFFERENT PULSE MODULATION TECHNIQUES Original Filed Feb. 5. 1946 8 Sheets-Shawl 6 1N VEN TOR.

MARCEL J.E. GOLAY Affari] Py Sept. 11, 1951 Original Filed Feb. 5. 1946 E GOLAY YsTE'II/I UTTLTZING SUCCESSIVE, ON TECHNIQUES 8 Sheets-Sheet 7 Y FIGB [2162 TO THE LAST OR NExT TO LAST SECTION OF DELAY LINE CORRECTED DELAY LINE z IzIN L SHAPINC SHAPINC SHAPINC AMPLIFIER AMPLIFIER AMPLIFIER To PULSE 2'02 52I2I 203 2I22 2'04 2I2s GENERATOR I IMULTIVIBRATORI R A. M. R A.M.l P. A.M. CONvERTER CONVERTER CONVERTER Y L2IIO I L2III I L2II2 FIG. lO 2504 fr INPUT SYNCHRONIZING PULSE CORRECTED PULSE SELECTOR GENERATOR DELAY LINE 250C \25O2 3OO2\ 3Com 300' SHAPINC SHARING SHAPINC AMPLIFIER AMPLIFIER AMPLIFIER TO SIMPLEx CHANNELS f f L.I=.I L R LF: FILTER FILTER FILTER CATED CATED CATED AMPLIFIER AMPLIFIER AMPLIFIER EVEN CHANNELS Laso kaso? Lat-,O8 RTM. k

TO ELM. oNvERTER 25I4 INVENTOR ODD CHTSELS ,ESIS l MARCEL JE. GOLAY 'TO BY PLM. 7`ZM'7 7% M/7@ CONVERTER 'mef/ Sept. 1l, 1951 M. J. E. GOLAY MULTIPLEX COMMUNICATION SYSTEM UTILIZING SUCCESSIVE,

DIFFERENT PULSE MODULATION TECHNIQUES Original Filed Feb. 5. 1946 8 Sheets-Sheet 8 FIG. II

I 310| I l I I I L|NE PuLsE FROM NSI sEcTIoN l oF DELAY LINE. ,I I

II I RIM. INTELLIGENCE PuLsEs i I L slocjuo I 'i I L Ism I sus :I |05 i i $021,? A I PLATE CURRENT oF I I PENTODE 27|? l3|04 I PLATE CURRENT OF TRIODE 2728 PLATE CURRENT OF TRIODE 2722 'l LINE PULSE FROM 'N13 SECTION I PLATE CURRENT OF PENTODE 27B' INVENTOR MARCEL JE. GOLAY Patented Sept. 11, 1951' .UNITED STATES PAT-ENT yopiates "-25567263" MULTIPLEX ecnmmoarioNsYslTEMnrl- :LI'zrNGq .sUCoEssIvE, DIFFERENT PULSE MODULA'TIoN-TECHNIQUES OMarc-e1 J'. niociay, Long Branca N. J.

.Original Aap,lication' AIebruar-y 55,'"1946, Serial No. 645,619. .Dividedfand this' 'application June "Z, 1947, fsefis1^No.751,s41

.(Granted .uliderg'the act voilldarch.3, 1883, as amended Aprilf, 1928;. 370 O. G. 757) v.electronic ldistributors.

:This application-is the divisional applicationof -.therparentapplication Serial No. 645,679,1ed AFebruary 125, 1946,l for CorrectedDelay Line.

/While theparent application discloses the dispersionless delay lines as well as the multiplex l.pulse communication system, this divisional application discloses only the multiplex pulsecommunication system. Therefore.. for a more fdetailed description of .the dispersionless delay lines, referencevis made to the parent application.

It is therefore -an object of this invention to provide a multiplexpulse communication system utilizing a delay line and a plurality of thermionic tubes as a multiplex electronic 4distributor for the system, and to provide -novel circuits for. synchronizing the .transmitting andreceiving distributors.

Still another object of this invention isto -provide a method of energizing the phase-,corrected delay lines.

Anotherobject of this invention is. to provide novel circuits for. converting. a. singleor a Vpluralityof audio. or video simplex signals intopulse- .amplitude-modulated signals; pulse-amplitudemodulated signals .into p l'ilse-length-modlated signals pulse-length-modulated signals into pulse-position-modulated signals at the transmitter, and reverse .conversions .onsignals .at .the

receiver.

As mentioned previously the .description-of the dispersionless .delay lines may befound in the .parent application and this application isre- .stricted only rto .the application of .a delay line having linear frequency phase characteristics to' a multiplex pulse communication system, the line .acting asv a component of' an electronic multiplex distributor for allocating .the necessary timev intervals to the respectivev channels.. at. a multiplex transmitter, and for separating these individual channels at the multiplex receiver,'whereupon .theseparated signals are directed tosimplex4 reeeivers.

`Thesse and other features of the invention y'ill ^be understood more vclearly from Vthe following ..5 detailed description and the accompanyingfdravvy.ings in which:

.Figure l is a blockdiagram;

Figures 2 and. 3 illustrate oscillograms offsignals;

'lFigures 4 `and lA are .the schematics 'f La. multiplex pulse-modulation transmitter;

Figure illustrates the matching relation- `ship'of Figs. -4 and 4A with respect 'to each other;

Flgure 5 is a block diagram; Figures 6 and 7 are the schematlcsof a' inliltiplex, pulse-modulation receiver;

Figure 8 illustrates the matching'relatin'sh'ip of Figs. 6. and 7 with respect to each other;

-Figures 9 and 10 are 'modied'blockV diagrams ofthe multiplex transmitter and receiver; 'and Figure 11 illustrates signal'oscillograms u'sed S to aid' the understanding of the functioningof "thereceiven Referring to Figs. l'through 7, they disclose an application of a corrected delay line to a multipl'e'xv pulse modulation system in which the delay "line acts as a multiplex distributoranda 'signalsampling device. At the transmitter aplurallty 30 -of'simplex channels is connected to'amultiplx transmitting station' through the multiplex distributor, and at the receiver the'received n'n'iltiplexY signals are separated into 'simplex signals 'by means of a synchronized multiplex distributor ad'directed into the respective simplex-'chan- "nel's, lIn either case the distributor isofan l'ectronic'- type keyed bythe delay line, 4Winch-"because 'of the rate of sampling 'of the-simplex "channels and large number ofthe' s'iniplsx- Chan- -nels-'f'multiplexed 'over a single UHF-channel, is "-islue'4 inost practical type of electronic-distributor that can perform the imposed task successfully.

'5Rfelin'g to Figure lfwhich isiabltitk` diagram 'of the transmitter, 4it .'discloses `a -plurality fof 45 simplex'lines 2102 through 2|09. The-number "f thesimplex channels may 'be`- smaller Torlar'ger than the number indicated tlieiigure,l eight 'hanls having been sele'cted' for illustrating: the fprlnc'ipleofoperation of the'finvention. Thej'sfim- 5o "plx 'lia'nnelsl I U2 through 2 I 09 may carry-either "addiofvideo or 'telegraph signals. 'The simplex "signalsare impressed on pulse amplitude modu- 'lators "(PAM) "2l I0 through '2i i1, which perfrm the function of sampling the'signals i-m- .55 pressed onthesimplex channels at' a sampling conductors 2121 through 2128 with the result that the modulators, which are normally nonconductive, are successively keyed by the delay v line, making one modulator operative at any given instant. Examination of the connections between the delay line and the generators discloses the fact that each generator is connected to alternately successive sections of the delay line so that an output signal from an odd generator, such as generator 2110, is followed by an output signal from anv even generator 2111. The outputs of the odd generators are connected to a common odd output bus 2130 while the outputs of the even generators are connected to a common even" output bus 2132. Thus, while the sampling rate in the modulators is determined by the delay time T, furnished by the successive sections of the delay line, as illustrated at 22-1 in Fig. 2, the successive signals on the individual output busses 2130 and 2132- are separated from each nother by a time interval T which facilitates the suppression of any cross modulation between the consecutive channels by allowing more time for the recovery of the PAM modulators, PAM-to-PWM converters 2138 and 2140, and of the PWN-to-PTM converters,- as will be explained more fully later. The signals appearing on the busses 2130 and 2132 are impressed respectively on conductors 2134 and 2136 connected respectively to converters 2138 and 2140 which transform pulse amplitude modulation (PAM) to pulse Width modulation (PWM). The outputs of the PAM-to-PWM converters are impressed on converters 2142 and 2144 which transform the pulse width modulation into pulse time modulation (PTM). These types of modulation, for the sake of clarity, are identified in Fig. 3. The respective types of modulation, i.`e., PAM, PWM, and PTM, being illustrated at A, B and C portions of the figure. The outputs of the PTM converters are impressed respectively on buifer ampliers 2146 and 2148 whose outputs are connected to a series circuit including a pulse Shaper 2149, a cathode follower 2150, a pulse amplifier 2152, a transmitter 2154, and a directive antenna 2156. A bus 214'1 is also connected to a synchronizing pulse generator 2120 through a buifer amplifier 2160 and the shaper 2149 and a converter 2158 so that generator 2120 impresses the transmitter-receiver synchronizing pulses on transmitter 2154 and antenna 2156 at a rate determined by the pulse rate of generator, 2120. The latter is under control of the delay line 2118, the last or the next-to-last section of line 2110 being connected to the generator over conductor 2162. Y

The operation of the system disclosed in Fig. 1 is as follows: the intelligence signalsare impressed on the simplex channels 2102 through 2109; the pulse generator 2120generates with the aid of the delay line 2118, Widely spaced pulses 2151 which are impressed on the delay line 2118 and pulse converter 2158., The synchronizing pulse 2159 is derived from the pulses generated by pulse generator 2120. (also see an oscillogram 2161 illustrated next to antenna 2156). The synchroniizng pulses are thus transmitted without any delay by the transmitter. The pulses 4 the progressively more yelayed pulses appearing at the outputs of the vespectivesections of the lineare used for making the PAMs 2110 through 21 1'1 operative for the interval of time determined by the duration, the amplitude, and the Wave form of the line pulses, and by the biasing potential normally impressed on the PAM converters. The rst keying pulse 2160 impressed on conductor 2121 is delayed by a time interval YT, Fig. 2,'by the first section of Ithe delay line,

which is interposed between a terminal 2164 of the line and conductor 2162, in order to provide L sufficient recovery` time thus permitting the relayed by the respective sections of the line, and

ceiver at the distant end to become prepared for properly receiving the succeeding channel pulses. PAM converter 2110 will therefore be allowed to transmit an intelligence signal 2163 from the simplex channel 2102. VThis intelligence signal 2163 is also illustrated.' as a signal 2202 in one multiplex channel signal illustrated in Fig. 2. The position of signal 2202 with respect tothe synchronizing pulse 2204 is determined by the amplitude of the signal existing on the simplex channel 2102 at the instant of. theappearance of the keying vpulse on conductor-2121. Transformation of pulse amplitude modulation appearing in the outputs of the modulators 2110 and 2111 is performed by two parallel channels each of whichv includes a PAM-to-PWMconverter, a PWM-to-PTM converter, and a buffer amplier. The outputs of the buffer amplifiers 2146, 2148, and 2160, are al1 combined in the pulse shaper 2149, and the output of the latter Ais eventually impressed on the UHF transmitter 2154and an tenna 2156. The transmitted signals are illustrated at 2161, Fig. 1, and at 22-3 ir Fig. 2, the marking or synchronizing pulses 2158 being transmitted at the beginning of each multiplex group of intelligence signals 2163.

It has been mentioned previously that it is desirable to have two parallelchannels for the conversion of the PAM signals into the PTM signals in order -to avoid cross talk and cross modulation between the adjacent simplex channels.

- The reason for this is as follows: the PAM generators, the PAM-to-PWM converters and the PWM-to-PTM converters include capacitive and inductive elements which will be variously energized in accordance with the amplitude of the impressed intelligence signals. After transmitting the sample signals these elements must be returned to their respective normal venergy levels before being exposed to the next sample signals to avoid the memorizing of the previously pro- -cessed signal, which, if not avoided, would result through 21 1'1 on a single converter channel; such modification, however, may introduce excessive crossv talk between the simplex channels if the guard spaces 2206 and 2208 are made too short.

As mentioned previously, delay line 2118 is normally a corrected line which has substantially linear phase characteristic. The advantages of having thev corrected line is that the pulses impressed on the" PAM- convertersfare-uniform in shape, and. which is at least as important, the

keying signals are substantially as sharp at the end of the line asf at its beginning. The pulses derived from, 4an uncorrected line lose their sharpness as they progress along the line, and they also undergo pronounced attenuation. Therefore, an uncorrected line may be used only if there is a large number of shaping amplifiers interposed between the line and the keyed tubes, which obviously complicates the system.

Referring now to Figs. 4 and 4A, whose relationship with respect to each other is illustrated in Fig. 4B, they disclose a schematic diagram of the multiplex transmitter whose block diagram is illustrated in Fig. 1. The corrected delay line 2| |8 is identified by the same numeral in Figs. 1 and 4. As in the case of Fig. 1, the line is connected to a pulse generator 2|20. The pulse amplitude modulators are included in a block 2400, while the PAM-to-PWM and PWM-to-PTM converters are illustrated in blocks 240| and 2402. Only the schematic diagram of converter 240| is fully illustrated in the gure, the second converter, because of its identity with the first one, being indicated in a block form. The two bulier amplifiers 24412 and 2443 are connected to the respective outputs of the PAM-to-PWM-to-PTM converters, and buffer amplier 2444 is connected to pulse generator 2| 20 over a conductor 2403, this connection also including a signal reecting line 2404. The combined outputs of the three buler amplifier-s 2442, 2443 and 2444 are impressed over a conductor 2405 on pulse shapers 2406, 2401 and 2408, the output of the last stage being impressed on the grid of a, cathode follower 2|50 which corresponds to the cathode follower similarly numbered in Fig. 1. The output of the cathode follower is connected over a conductor 2409 to pulse ampliiier 2| 52. and transmitter 2| 54 and antenna 2|56.

Proceeding now with a more detailed description of Fig. 4, pulse generator 2|'20 comprises a pulse-controlled multivibrator circuit 24m-24| l. Triode 24|0 is connected with its cathode-plate circuit across a grounded bus 24|2 and a +B bus 24| 3. The cathode of the beam tube 24|I is grounded through a conductor 24|4, coils 24| 5 through 2423 of the delay line and a line terminating resistance 2424, while its plate is connected to bus 24|3 through a resistance. The grid of triode 24|0 is connected over condenser 2425 and a conductor 24'26 to a junction point 2421 formed between the last and next-to-last sections of the delay line. Whether the connection of this grid is to the junction point 242'! or to the junction point 2428 depends upon whether the ascending or the descending portion of the signal will be instrumental in triggering the multivibrator. With the connections illustrated in the figure, triode 24|0 is 'tobe tri-ggered by the descending portion of the positive pulse in the delay line. As in the case of the multivibrators. the control grid of one tube is coupled tothe plate of the other, and vice-versa; the grids are also connected to bus 24|3 through grid resistors. The output of the multivibrator is impressed on the artificial line 2| I8 which is shunted by the impedance a correcting series circuit consisting of resistance 2430 and a condenser 243|. Its output is also coupled through a condenser 2432 and a resistance 2433, conductor 2403 and a coupling condenser 2434 to .the .grid of buffer amplifier 2444 for combining the synchronizing pulses with the intelligence pulses appearing in the outputs of the amplifiers 2442 and 2443 in a common l cathode resistor 2435. The chan- .Y

nel of the transmitter also includes a reflective delay line 2404 which transforms, with the aid of a reflected pulse, the pulse impressed on the grid of triode 2444 into a pulse 2429. The delay line 2||8 connected to pulse generator 2|20 is of the type in which the linear frequency phase relationship through the line is obtained by introducing a plurality of corrective capacities 2431 through 2440, 2456, 2466 and 2461. The remaining condensers 244| are for completing the usual ladder type configuration of a delay line. The junction points of the delay line are connected by means of variable coupling condensers such as 2445, 2448, etc., to the suppressor grids of eight. pentodes. which comprise the gated PAM stages ofthe transmitter. They correspond to the PAM stages 2||0 through 2||1 in Fig. 1. Since the connections of all PAM stages are identical, only the connections of a single pentode 2458 will be given.- Its cathode is connected through a resistor2452 to a grounded bus 2453 and its anode is connected to bus 2454 for the odd simplex channels, this bus corresponding to bus 2|30 in Fig. 1. The outputs of the even pentodes, such as pentode 2455, are all connected to bus 2451 for the even simplex channels, this bus corresponding to bus 2|32 in Fig. 1. The screen grids of all pentodes are connected through resistances, such 'as resistance 246| to the positive bus 2462 which supplies the necessary positive potential to the screen grids and the plates, the plate connections being completed through plate resistors 2463 and 2464. All simplex channels are provided with copper oxide rectiers, such as 2428 and 2432, which. together with the biassing resistors 2436, 2448, 2455 and by-pass condensers 2410 and 2495, act as amplitude limiters for the simplex signals. The simplex channels 2|02 through 2|09 are connected to the control grids of the pentodes through coupling condensers such as condenser 2459; grid resistors, such as 2460, connect the control grids to a common grid bus 2465, which is connected to a potentiometer 2468; this potentiometer impresses a sumciently high positive potential on the control grids of the pentodes to produce class A amplification in the pentodes of the simplex channel signals. Resistor 2452 serves as cathode blassing resistor and its shunting condenser serves to prevent degeneration of the audio frequencies of the simplex channels. The suppressor grids of the pentodes, besides being connected to their respective delay line coupling condensers, are also connected through the suppressor grid resistors, such as resistances 2469 and 245|, to a common, grounded suppressorgrid-bus 2410. The potentials impressed on the suppressor grids of the pentodes are such as to make their plates normally nonconductive, and the plates are made conductive and thus are permitted to respond to the simplex signals only when a positive signal is impressed on their suppressor grids by the respective sections of the delay line. Thus the gated PAM stages perform a dual function: they act as an electronic distributor for the signals appearing in the simplex channels at a. rate determined by the parameters of delay line 2| |8, and they also transform the audio signals into the PAM signals. The odd and even channel busses are connected to the PAM-to-PWM-to-PTM converters 240| and 2402 where the PAM signals are converted into the PTM signals. Referring to the connections of the lower converter 240 the connection between the odd bus 2|54 and the grid of triode' 241| -is accomplished through a coupling condenser 241-2 and a grid resistor 2413, the latter connecting the grid to the positive bus 2462. Triode 241| is normally fully conductive because of the positive potential impressed on its grid by bus 2462 through resistance 2413. The cathodes of triodes 241| and 2414 are grounded through a common cathode resistor 2415, and the space current of triode 241| is normally suiiiciently high to so raise the common cathode potential of triodes 241| and 2414 that triode 2414 is normally cutoff. The plate of triode 2414 is connected through a resistor 2459 and in parallel coils 2416, 2411 and 2418 and resistor 2449 to the +B bus 2462. The coils and condensers 2419 through 2482 form an out of phase reflecting line producing .the PWM-to-PTM conversion of signals. as will be described later: resistor 2441, connected across the line input, is designed to dissipate the signals reflected from the other end of the line. The grid of triode -2414 is connected to a biassing potentiometer 2483 which impresses a positive potential on the grids of four triodes: 2414, 2442, 2443 and 2444'. The latter three grids are connected to the same point on the potentiometer through resistors 2484, 2485 and 2486. The grid of triode 2442 is connected through a coupling condenser 2481 to a junction point 2489, while the grid of triode 2443 is connected to a similar point in the output of the even PAM-PWM- PTM converter. The outputs of the three buffer ampliiiers are combined in the common cathode resistor '2435 and are impressed on the cathode of triode 2406 whose grid is connected to a potentiometer 2490 and whose plate is connected to a +B bus 249|. The plate of triode 2406 is connected through a blocking condenser to the grid of shaping amplifier 2401, this grid being connected also to potentiometer 2490. The cathodes of the triodes 2401 and 2408 are grounded through a common resistor 2492. A capacitive coupling between the plate of triode 2408 and the grid of cathode follower 2|50 causes the latter to follow the plate potential of the former, and a cathode resistance 2493 of the cathode follower is connected to conductor 2409 leading to the amplifiers 2 |52, transmitter 2 |54 and antenna 2|56.

The operation of the transmitter, Fig. 4, is as follows: The pulse generator 2| 20 is a pulsecontrolled multivibrator whose parameters are calculated so that it impresses, during the conductive state of tube 24| I, a, pulse of proper duration on the delay line 2| |8. In one of the transmitters built by me multivibrator 2|20 has a free-running repetition rate somewhat lower than 10 kc., l0 kc. being the desired repetition rate of the system. The connection 2426 from the penult end of the delay line to the grid of tube 24H1 serves to control this multivibrator so as to make its actual repetition rate exactly equal to this desired repetition rate. When the pulse generated by the multivibrator has reached the junction point 2421 of the artificial line and the regenerative connection 2426 towards the end of its travel along the line, the voltage of the grid of tube 24|| is approaching that level at which tube 24|| is ready to become conductive again. The eiect of the multivibrator-controlling pulse 2494, reaching the coupling condenser 2425, is momentarily to raise the voltage on the grid of tube 24|0, and then to lower it during its downward excursion. Since grid 24|0 draws slightly more grid current during the upward excursion 91.91.11 it the. eher@ n wneensgii .11%-

creased during this period, and the downward excursion of pulse 2494 will lower the grid voltage of tube 24|0 because of the discharge of condenser 2425 at this instant with the concomitant generation of a positive pulse 2495 at the plate of tube 24|0. This positive pulse is impressed on the grid of tube 24| making it conductive because the potential on the grid of triode 24| as it will be recalled, had almost reached at this instant that levelA which makes tube 24|| conductive, the parameters of the multivibrator having been adjusted so as to make the free-running repetition rate of the multivibrator slightly longer thanthe desired repetition rate of the system. When tube 24|| is rendered slightly conductive, the multivibrator is immediately triggered and impresses a positive pulse 2496 on the main delayline. The positive pulses 2496 are impressed, after the introduction of fixed time-lags by the respective sections of delay line 2I|8, through the coupling condensers such as condensers 2445, 2446, etc., on the suppressor grids of the pentodes, which up to this instant had no plate current. Considering pentode 2458, it makes the plate of the latter momentarily responsive to the signals impressed by the simplex channel 2|l'l2 so that a sampling pulse of the simplex signal appears in the plate output of pentode 2458 as a negative signal 2491. The amplitude of this signal will be proportional to the amplitude of the simplex signal during the keying intervalof pentode 2458. The operation of the remaining pentodes is identical to the operation of pentode 2458. The variable amplitude signals, such as 2491, of the odd simplex channels are impressed on the grid of triode 241| through coupling condenser 2412. Triode 241| is normally fully conductive because of the full plate potential impressed on its grid by |B bus 2462 through'grid resistance 2413. When negative signal 2491 is impressed on the grid of this triode, it is rendered less conductive. Any decrease in the conductivity of triode 241| produces a corresponding decrease in the voltage drop across cathode resistance 2415 with the result that the ,potential of the cathode of triode 2414 is lowered to the' same extent. The grid of triode 2414 is-conneeted to a iixed biasing potential-i.- e., potentiometer 2483. Therefore, when the potential of the cathode of triode 2414 is lowered because of the decrease in the conductivity of triode 241 triode 2414, having fixed biassing potential, becomes conductive, a negative rectangular pulse 2488 appearing in its plate circuit. This is impressed through condenser 2498 on the grid of triode 241| so that this grid will be subjected to the dual action, the first being that produced by the negative pulse 2491, and the second action being produced by the negative pulse 2488 transmitted to this grid through condenser 2498 from triode 2414.r` The latter action is of the one-shot multivibrator type; theV two negative signals combineA and render triode 241| completely nonconductive, the duration of the nonconductive state oftriode 241| being a function of the amplitude of the negative signal 2491. The time constants'of the resistance-condenser combination 2464, 2413, and 2412 are so adjusted that the negative PAM signals of maximum amplitude are capable of keeping triode 241| nonconductive throughv the greater portion of the interval allotted for the simplex channel, whereas the negative PAM signals of minimum amplitude cause triode 241| to stay nonconductive be a function of the amplitude of the PAM signal. When tube 241| has become sumciently conductive, the reverse multivibrator action takes place through cathode resistance 2415, which again lowers the potential of the cathode of triode 2414 so that it becomes again nonconductive.

Thus the effect of the variable amplitude PAM signal 2491 is to generate a substantially rectangular pulse 2488 of variable duration and therefore the PAM-to-PWM conversion takes place in the circuits of the triodes 241| and 2414. The' PWM signal is impressed on the delay line including the coils 241B, 2411, 2418, and the associated condensers, the termination of this line being such that the rectangular pulse 2488 impressed on the line is reflected 180 outof phase:

by the line termination back to the junction point 2489; the time-constant of the line is such that' the negative rectangular signal 2488, and the positive reflected signal combine in part at the junction point 2489, and since the reflected signal is a delayed signal, the summation of these two signals at this `iunction point produces the signal illustrated at 2499. Since the position of the positive signal with respect to the negative signal will be a function of the duration of the rectangular signal 2488, the-positive signal will be the desired PTM signal, the position of the positive portion of this signal with respect to the xed position of the negative portion be.

ing substantially linear function of the amplitude of the PAM signal 2491. Thus the transformation of the PWM signal 2488 to PTM signal 2499 takes place at the junction point 2489, triode 2414 in combination with the reilecting delay line performing the function of the PWM-to-P'IM converter.

The next required step is to suppress the undesired negative portion of signal 2499 and to transmit the useful positive PTM. portion to the transmitter. This is accomplished by impressingl the entire signal on the coupling condenser. 2481 which is connected to the grid of buier 4amplifier 2442. Ampliiier 2442 is normally nonconductive, the positive potential impressed on the grid of shape all signals before their transmission by anthe amplifier by potentiometer 2483 through the grid resistor 2484 being normally overcome by the positive potential impressed on its cathode by the cathode resistor 2435 because of the space current normally ilowing through the normally distributor of the transmitter.

The operating cycle described thus far related to the transmission of the intelligence signals from the oddly numbered Ysimplex channels. The transmitting cycle for the evenly numbered channels is identical to that just described except that a separate PAM-to-PWM-to-PTM converter 2402 is employed by these channels. The output of this converter is impressed on triode 2443, and it is in the output of this triode, and more particularly in the resistance 2435, that the signals "from the odd and even channels are combined Y for their transmission to the receiver.

In order to maintain strict synchronism between the transmitter and the receiver, synchronizing pulses 2429 are transmitted to the re- 'ceiver at the beginning of each sampling cycle frso that the electronic distributor at the receiver is kept in strict synchronism with the electronic This is accomplished .by impressing a portion of the output of multivibrator 2120 over condenser 2432 and re- .sistance 2433 on conductor 2403 and pulse-forming, reflective, delay line 2404. When rectangular pulse 2496 is impressed on reflecting line 2404, the latter produces a 180 out of phase reflected pulse at the vend of the line which is terminated to'this eiect, and the leading portion of the reflected` negative pulse combines with the lagging portion ofthe positive pulse 2496, the two combined'portions neutralizing each other. The resultant pulse 2429 consists of a positive pulse and a negative pulse, which are both impressed on the grid of triode` 2444 over conductor 2403 and condenser 2434. .Triode 2444 is normally nonconductive because of the positive potential normally impressed o n its cathode by the cathode resistance 2435, thegridof this triode being connected to potentiometer 2483. The action of the triode 2444 is similar to the previously described action of triodes A2442v and 2443, the potentials normally impressed on their grids and cathode being mutually equal. When the positive'portion of the synchronizing pulse 2429 is impressed on the grid of triode 2444 itis rendered conductive which in turn raises-the potential of the cathode of triode 2406. From this-it `follows that the synchronizing pulse as well as all intelligence signals are combined vin the cathode resistance 2435, and therefore the shaping ampliers 2406,

2401, 2408 and the cathode follower 2|50 preconductive triode 2406 whose grid is connected toi-.l

a xed positive potential appearing on potentiv ometer 2490. Because of the normally nonconductive state of triode 2442, the negative portion of the PTM signal 2499 has no effect on this tri- Referring now to Fig. 5, it discloses the block In the receiver the nals after detection, conversion and amplification are impressed on a selector 2 500 which selects the synchronizing pulse and impresses it on ode, and only the positive portion is capable ofi# making is conductive. Since amplier 2442 may be considered as a cathode follower, it renders triode 2406 nonconductive, positive potential being impressed on the cathode of the latter by the a pulse generator 2502; the latter is a pulse-controlled multivibrator, the synchronizing pulses 'controlling its timing. The positive pulses 2503 A appearing in the output of the pulse generator cathode resistance 2435 when the PTM signal-vv makes the cathode follower 2442 conductive. The positive signals appearing in the plate circuit of triode 2406 are impressed on the grid of triode 2401, then triode 2408, and then cathode follower 2| 50, which in turn energizes the transmission-f are impressed on a corrected delay line 2504 and Ithe sginals appearing in the successive stages of this line are used for making the gate ampliiiers 250B through 25| I operative in synchronism with the appearance of the respective simplex channel signals on their grids. Thus, these ampliers, together with the corrected delay line, act as an electronic distributor for the multiplex channel -signals impressed upon them through flip-flop multivibrator 25|4 and 25|6. Each ilip-fiop multivibrator is connected to the output of the inverter stage of selector 2500, which impresses Aacts as a PTM-to-PWM converter.

negative signals 2520 on both multivibrators. Both multivibrators receive all signals impressed on them but one responds to the odd simplex signals only, while the other responds to the even simplex signals only, thereby causing the odd simplex signals only to appear on bus 2524, while the even simplex signals appear on bus 2522. Furthermore, each simplex signal in the even or odd sequence will affect only the amplifier to which it is assigned because the latter is rendered operative at this instant by the distributing pulse from the delay line 2506, all other amplifiers at that instant remaining inoperative. This is obtained by making the parameters of line 2504 equal to the parameters of the delay line 2| I8, Figs. 1 and 4, and by transmitting the line actuating pulses 2503 from the transmitter so that the line actuating pulses at the receiver are synchronized with the simplex signals. Thus amplier 2506 will be rendered operative by the delay line 2504 at that instant when the simplex PTM signal from the simplex channed #I appears on bus 2522. This simplex signal appears in the output of amplier 2506 as a PWM signal, which The PWM signal is impressed on a. low pass filter 2528 which transforms it into an AM intelligence signal and transmits it to an outgoing simplex channel 2530. 'I'he same cycle takes place in the remaining simplex channels 253| through 2531.

Figs. 6 and '7 disclose the schematic diagram of the receiver. The relationship of these figures with respect to each other is illustrated in Fig. 10. the two figures being connected to each other over three conductors 2600, 260|, and 2602, similarly numbered in both iigures. The signals received by a receiving antenna 2603 are impressed on a receiver 2604 where they are detected and amplied, whereupon they are impressed as positive signals 2605 on the grid of a triode 2606. Triodes 2606 and 2608 act as pulse shaping amplifiers, triode 2608 being normally fully conductive because its grid is connected to the positive voltage of a potential divider 26| 0, While the grid of'triode 2606 is connected to ground through a grid resistor. The positive signals 2605 are inverted and impressed as negative signals 26I4 on conductor 2600. They also appear as positive signals at the cathode of triode 2608 thus making this triode nonconductive. Therefore, they are impressed as 'positive signals 2609 on a coupling condenser 26|6 and a short, reiiectionless delay line 26 I8 having terminating resistances 26 I 9 and 262|. The output of the line is connected to a coupling condenser 2620 and the two condensers 2620 and 26| 6 are connected to the gridof a triode 2622. The signals lappearing on the grid of triode 26'22 are illustrated at 2624 and the normal biassing level of this grid is illustrated by a dotted line 2625. The delay introduced by the line is calculated to have the duration greater than that of the channel pulses but smaller than that of the synchronizing pulses, as illustrated at 2632 and 2633, signal 2633 being the reflection of the original PTM signal 2632. For this reason the direct and the delayed synchronizing pulses partially combine to produce the peaked pulse 2626, and because of the relatively low negative biassing potential level 26'25 only the peak portion 2626 of the pulse makes triode 2622 conductive. Since the simplex signals do not combine as illustrated at 2632 and 2633, they are blocked at triode 2622 and have no effect on the circuits connected to the output of triode 2622. The cathode of triode 2622 is connected to ground over a cathode resistance 2628, and it is also connected to the cathode of a triode 2630 Whose grid is connected to the positive voltage of a voltage divider formed by resistances 2620 and 263|. Therefore, triode 2630 is normally fully conductive and its conductive state keeps the cathode of triode 262'2 at a sufliciently high positive potential to keep triode 2622 normally nonconductive. The peak portion 2626 of signal 2624 appears as a negative pulse 2634 in the plate circuit of triode 2622 and is impressed on conductor 2602, a coupling condenser 2100, and the grid of a triode 2102, which, together with a triode 2103, forms a pulse-controlled multivibrator circuit. Since the grid of triode 2102 is connected to the positive bus 260| over a resistance 2104, triode 2102 would be normally fully conductive if it were not for a condenser 2101 which connects the grid to the plate of triode 2103. The same is true of triode 2103 Whose grid is connected tothe same bus over a resistance 2105 and to the plate of triode 2102 through a coupling condenser 2106. Because of the condensers 2106 and 2101, the potentials on the grids are now determined by the state of charge on the condensers 2106 and 2101. and Whether the condensers are charging or discharging. When negative signal 2634 is impressed on the grid of triode 210'2, this triode, which will be assumed to be conductive at the time, is rendered less conductive so that a positive signal is impressed on condenser 2106 and the grid of triode 2103. ItY will .be assumed that triode 2103 has almost reached that state which makes it conductive at that time` Therefore positive signal 2108 makes triode 2103 conductive and the multivibrator is triggered to its second state of equilibrium for a time determined by its parameters which are so chosen that a positive pulse 2109 of the desired duration is impressed on delay line 2504 by means of input impedance 21I0-21I I. At the end of this cycle the multivibrator reverses to its previous state, and the grid voltage of triode 2103, which is now cut off,- begins to rise, the time constant of the multivibrator, as mentioned before, having been so chosen that this voltage approaches that needed for making triode 2103 conductive when the next synchronizing signal is received. It thus will be noted that the circuits of the receiver described so far select the synchronizing pulses and impress them on the corrected delay line 2504: The intelligence signals do not have any effect on the delay line 2504 since they do not appear in the output of triode 2622 because the high blocking potential impressed on the grid of triode 2622; moreover, While the relatively long synchronizing pulses produce superimposition of the direct and reiiected signal as illustrated at 2626, the intelligence signals which are of shorter duration produce a series of direct intelligence signals. such as signal 2632, and a series of reected signals such as signal 2634, the direct and the reflected signals being spaced apart as illustrated in the oscillogram; therefore they areY all blocked at triode 2622 and have no eifect on the )corrected delay line 2504.

Proceeding now with the description of the multiplex distributor of the receiver. the control grid of a pentode 21|2 is coupled to the rst section of the delay line through a condenser 21|( and resistances 21| 6 and 21| 1I resistance 21I6- controlling the maximum amplitude of the signal impressed on the grid. Resistor 21I1 con-- nects this grid to a grounded bus 21I5. The screen grid 'of the pentode is connected to a screen grid bus 2118. One end of this bus `iscoupled through a condenser 2120 to the grid of a triode 2122, while its opposite end is connected through a resistance 2123 to a +B bus 2124. The suppressor grid is connectedto a suppressor grid bus 2125, this bus being grounded through a grid lead resistance 2119; the bus is also coupled through condensers 2126 and 2121 to the plate of a triode 2128. .Condenser 2121 is shunted by a resistance 2130; a similar connection 2131--2132 exists lbetween the grid of vtriode 2128 andl the plate of triode 2122, the condenser-resistance combinations 2121-2130 and 2131-2132 A comprising the well known flip-dop multivibrator connections between the .grids and the vplates of the two triodes. The cathodes of the triodes 2122 and 2128 are connected tothe grounded bus 2115 through a common cathode resistor 2134. The grid of triode 2128 is connected overa coupling condenser 2136 to conductor 2600 which impresses the negative synchronizing and simplex signals 2614 on the grid of this triode. From the connections of the triodes 2128 and 2122 it follows that they represent the double stability or flip-flop version of the Echles-Jordan multivibrator circuit, .the modiication residing in the fact that the grid of triode 2128 is connected to one source of pulses, while the grid of triode 2122 -is connectedtothe-other sourceofpulses. .i

The operation of this iiip-op multivibrator and .of pentodeV 21I2.is;as vfollowsz'it will be assumed that the normal state lof the multivibrator is such that triode 2122 is conductive and triode 2128 nonconductive,..a conditiomwhich will be found to exist `because the last .preceding signal applied to the grid of triode 2128 over conductor 2600 by inverter 2606 was either-a negative simplex pulse or a negative *synchronizing pulse. When the delay line 2504-impresses a positive pulse 2140 on condenser 2114, the control grid of pentode 2112 draws a small grid current. This grid current somewhat flattens the peak portion of the pulse impressed upon itby the articial line because of the voltage drop in resistance 2116, which limits the positive potential appearing on the grid to a predetermined maximum value. When pentode 2112 is rendered conductive, a space current flows from the -cathode to the plate, and through resistance 2141 to bus 2124. The screen grid current also increases thus lowering the potential of bus 2118, a negative pulse being transmitted tothe grid of triode 2122 through condenser 2121i.l When the potential of the grid of triode 2122 is thus made lower than the potential normally impressed upon it at the time when triode 2128 is nonconductive and triode 2122 fully conductive, triode "2122 is made less conductive, and triode 2128 becomes conductive because of multivibrator action thus initiating the triggering of the flip-flop circuit, which results in the triode 2128 becoming fully conductive and triode 2122'nonconductive. As triode 2-128 becomes fully conductive, a. negative pulse is impressed by the plate circuit of triode 2128 on the suppressor grid bus 2125 through the condensers 2121 and 2126 and through this bus on the suppressor grid of pentode 2112. This negative pulse cuts off the plate current of pentode 2112, thereby causing a slight increase in the screen grid current, and a corresponding decrease in the potential of the screen gridjbus 2118 because of the increase in the IR drop across resistance 2123 connecting the screen bus to the +B bus 2124 This lowering of the screen grid bus potentialA is" 14 i transmitted to the grid of triode 2122, which in turn lowers the screen potential still farther, thus obtaining a regenerative action which assists the retention of the nip-nop circuit in its new state of conductivity, i. e., triode 2122 being nonconductive and triode 2128 fully conductive. The new condition just described will persist until the negative simplex pulse from the first simplex channel, which is made to appear during the keying interval of pentode 2112, is impressed on the grid of triode 212B.v This pulse causes the flip-flop circuit to reverse its electrical position, triode 2123 becoming cut-oil. A positive pulse now appears in its plate circuit which is impressed on the suppressor grid of pentode 2112 through the condensers 2121 and 2126 which makes the plate of pentode 2112 to draw current again. This reappearance of plate current is accompanied by a slight decrease in the screen current, and consequently a slight rise in the screen voltage which is transmitted through condenser 2120 to the grid of triode 2122, thus regeneratively assisting the above reversal of conductivity in the multivibrator. It will be noted that the militivibrator has thus reverted at this instant again to its original position, namely, 2128 cut-off and 2122 fully conductive, which is the one assumed at the beginning of this description. The state of theplate conductivity of pentode 2112 will now continue until the original line pulse disappears, at which time the plate and the screen grid of pentode 2112 ate both cut-off. It will be noted that the blocking of pentode 2112 does not affect the ilip-op circuit since the resulting application of a positive pulse to the grid of the already fully conductive triode 2122 cannot make it more conductive. It is now proper to stress the fact that the duration of the last conductive state of the plate of pentode 2112 will vary linearly with the time of occurrence of the simplex channel pulse with respect to the marker pulse, thereby generating a width-modulated pulse in the plate circuit of pentode 2112, which after being impressed on condenser 2142, conductor 2143 and subsequent suitable low pass filtering enables the reproduction of the original audio or video signal of the first simplex channel sent by the transmitter. This separation of the simplex signals and their demodulation is reproduced at the succeeding channels and since it is identical to the functional cycle of channel #l given above, needs no repetition. It should also be noted that the negative marker pulse does not affect the position of the flip-flop circuit, since a negative pulse applied to the grid ofv triode 2128, which had already been thrown into the nonconductive state by the last simplex pulse, has no eilect on the multivibrator. Likewise, the odd channel pulses Will not affect the position of the even channel flip-nop circuit and vice-versa.

In the description of the functional cycle of pentode 2112 and of thevip-op multivibrator 2128-2122, it has been stated that the pentode 2112 is made conductive when the keying delay line pulse is impressed on its control grid, this pulse appearing in the simplex channel as a constant frequency pulse, the frequency of this pulse being determined by the sampling rate of the multiplex system. When this constant frequency pulse interferes with the intelligence signal which is, for instance, the case when the sampling rate is in the audio frequency range and the intelligence signals are audio frequency signals, it becomes necessary to suppress the signal in the simplex channel by means of an additional band pass ilter. Since such illtering of the sampling frequency in the simplex channels is known in the art, this additional filtering has not been indicated in any of the diagrams. Ihe functional cycle of the multivibrator 2144 and of pentode 2112, by the way of a summary of the functional cycle of these elements, is also illustrated in Fig. 11, by means of oscillograms of the signals appearing in these circuits.l Referring to Fig. l1, a line pulse 3101 is generated by the first section of the line and impressed on the control grid of pentode 21 I2 through coupling condenser 2114. The immediate effect of this pulse is to make pentode 2112 fully conductive as illustrated by the rising portion 3102 of the plate current in the pentode. However, making of this pentode fully conductive lowers the potential of the screen grid bus 2118 and as a result of this lowering of the screen grid bus potential the multivibrator is iipipped into the state of conductivity indicated at 3103 and 3104, triode 2122 becoming nonconductive and 2128 conductive. The conductive state of triode 2128 lowers .its plate potential and since this plate is coupled to the. suppressor grid of pentode 2112, the plate current of the latter is cut oi as illustrated at 3105. The multivibrator has been thus flipped into the position which allows it to respond to the PTM intelligence pulse, this .ilipping having been performed by the line pulse impressed on the pentode. Accordingly, when the negative leading edge 3106 of PTM intelligence pulse is impressed on the rigid of triode 2128, it flops' the .multivibrator back into its normal state of con- -ductivity as illustrated at 3101 and3108 with ltriode 2123 becoming nonconductive and its plate voltage rising to the potential of the +B bus. This rise of plate potential is transmitted to the suppressor grid of -the pentode with the result that the full plate current again flows in this pentode as illustrated at 3109. The multivibrators parameters are so adjusted that it remains in this state of conductivity when the PTM signal disappears, as illustrated atr3ll0, and, therefore, in spite of the disappearance of the PTM signal, pentode 2112 remains conductive, as illustrated at 3111, until the disappearance of the line pulse 3101 which makes pentode 2112 again nonconductive, as illustrated at 3112.

-Making pentode 2112 nonconductiveproduces a corresponding rise in the potential of the screen grid bus 2118 which has no effect on the multivibrator since triode 2122 is already fully .conductive as illustrated at 3113. Examination of the current pulses produced in the plate circuit of pentode 2112, which are illustrated at 3102, 3105, 3109, 31 11 and 3112, reveals the fact that a pulse -3102--3105 of fixed amplitude and i-lxed duration is produced first, and this pulse is followed by a PWM pulse 3109-3111-3112, the position of the leading edge 3109 of the latter being determined by the time of occurrence of the PTM pulse 3106. This PWM pulse is impressed on the previously mentioned illter where it produces the desired intelligence signal. The fixed amplitude and xed duration pulse 3102-3105, is illtered out by the previously mentioned hand pass iilter. Fig. 1l also illustrates the fact that the succeeding PTM intelligence pulse 3114 has no effect on pentode 2112 nor any subsequent odd pentodes because none of these pentodes are under the influence of the positive pulses from the corrected delay line 2504. The intelligence -pulse 3114 does not have any eiIect on the multivibrator 2128-2122 either because triode 2128 is alreadynonconductive, as illustrated at 3115, and as a consequence all evenly numbered PTM intelligence signals are blocked by the odd multivibrator 2144. However, they will get through the even multivibrator 2145 and one of the pentodes, in this instance pentode 2113, pulse 3114 being the pulse from the second simplex channel.` Fig. 11 also illustrates the idealized oscillograms of the signals which make pentode 2150 conductive, the signals produced in this pentode being illustrated at 3116 and 31 1'1. The line pulse which is impressed on pentode 2150 by the third section of the delay line 2504 is illustrated at 3118 and the PTM intelligence pulse transmitted from the third simplex channel is illustrated at 3119. The behaviour of the multivibrator 2144 is illustrated at 3120 and 3121. Examination of these signals reveals the fact that they represent no more but a repetition of the functional cycle that has taken place previously in multivibrator 2144 and in pentode 2112.

Thus at the receiver the multivibrators 2144 and 2145 block the synchronizing pulses and the intelligence signals from the odd simplex channels produce PWM signals in the respective odd pentodes, while the evenly numbered simplex channels produce similar signals in the evenly numbered pentodes with the aid of the even multivibrator 2145.

-While in the described applications of the delay lines the keying signals for controlling the simplex .channelsarev derived from each successive sec- 'tion of the delay line, there may be cases in which the signal thus derived is not suiliciently sharp to perform its selection properly. In such cases it'wili be advantageous to utilize a delay line having two or three sections or even a greater number of sections from each simplex channel so ing pulses, may be'also obtained by deriving the keying pulses from each successive section of the delay line, as described previously, and by impressing these pulses on shaping amplifiers, as illustrated in Figs. 9 and 10. Fig. 9 illustrates a portion of the block diagram of the transmitter of Fig. 1, with the similar elements being similarly numbered in both figures. The delay line 2118 in both gures has the same total number of sections and there is the same number of simplex channels; the wave-form of the 'keying pulses is improved by inserting shaping ampliners 2801. 2902. 2303, etc., between the line and the PAM converters. The same method'of improving the keying pulses at the receiver is i1- lustrated in'Fig. 10, in which case the shaping amplifiers 3001, 3002, 3003, etc., are inserted between the line and the gated amplifiers 2506, 2501, 21508, etc.

adjacent pulses generated by the adjacent .line sections. The advantage of 'such vaiirangenient resides in the fact that since the coupling .condenser is a two-section variable condenser, it, is possible to vary 'the occurrence. of `the keying puise by varying the degree oficoupling of the two sections of the coupling condenserto the adjacent sections. When this degree of coupling is varied so as to produce a closer coupling between the leading section of the line, the occurrence of the resultant keying pulse lis made earlier and when the degree of couplingis reversed --the resultant keying pulse is delayed. While'this-is the preferred arrangement for .coupling the delay line with the pentodes, it'is 'to be'understood that coupling of the pentodes to two adjacent'sectins" may be dispensed with, in which case they are coupled only to a single section. The' limitation of this arrangement resides in the fact l:that the ling along said line, first and second multiplex busses connected to the outputs of said tubes, the outputs of the veven-numbered tubes being connected to said rst bus and the outputs of the odd-'numbered tubes being connected to said second bus,"the respective sections of said line making said-tubes periodically operative to trans- `I0rmthesimp1ex signalsappearing in Said Simplex` channels into pulse-amplitude-modulated 'signals atsaid busses, apulse-amplitude-modula- A1x5 tion-to-pulse-width-modulatiori converter and a pulse width -niodulation t0 pulse timemodulation converter vin series Ltherewith connected to each of said busses, and a transmitter having aconnection to theloutputs of the last adjustment of the time-of occurrence ofithelkey--, 20 tWO COIlverteIS and t0 said generator, said transing pulses is then no longer available, and-should' it be necessary to make slight 'adjustments in the time of occurrence of -the keying pulses; it will benecessary to obtain them by adjusting the inductances and the capacitances ofwthein'di-. vidualline sections. The latter arrangement is` izes several sections for each" simplex channel,"

which is, as mentioned previously, maybe resorted to inorder to improve the wave-form of the keying pulses, the individual sections-of the v mitter transmitting said simplex signals as a series of; pu1 S e-time1moduleted signals preceded f by a transmittedjsynchronizing signal from said generator,A

'2. A 'multiplex transmitter according to claim l, wherein said 'bussesoomprise a source 'of negative pulse-amplitudr-mo'dulation signals, and said pulse amplitude'- to pulse width modulatOn Converter includes, a one shot multivibrator 3o connected said source, said multivibrator including a first normally tullyconductive triode with the grid of said .iirsttriode being connected to the positive terminal oi asource of potential ,through a grid resistance. and to .said source coupling condensers are again connected to the.35 ,.th i'ough an .input condenser. a .Second normally adjacent sections as illustrated in Figs. 4 and 7,`

suiiicient time adjustment of the keying pulses being obtained with this type of connection even though the delay furnished by each section has been reduced. A

The multiplex distributors hate been trated with the individual pentod tube's being used as individual electronic switches for the respective simplex channels. While this is one possible arrangement, it is to be understood that the pentodes may be replaced with other known electronic switching circuits, such as those disclosed in the applications for patent of William A. Huber et al., entitled, Radio Object Locating System, Serial No. 478,862, led March l2, 1943, and William A. Huber et al., entitled, Radio System, Serial No. 518,934, led January 20, 1944.

In the disclosed multiplex pulse-modulated system, the transmitted signals are pulse time modulated signals. It is to be understood that the multiplex distributor per se is applicable to the systems using any type of pulse modulation as a means of transmitting intelligence, and therefore the additional conversions of one type or" pulse modulation into the other type illustrated in Fig. l, such as from PAM-to-PWM, and PWM-to-PTM, may be omitted if pulse amplitude modulation is selected for transmitting the intelligence signals.

.Vhe the invention has been described with reference to several particular embodiments, it will be understood that various modifications of the apparatus shown may be made within the scope of the following claims.

I claim:

1. A multiplex transmitter including a synchronizing pulse generator, a phase-corrected, multisection delay line connected to said generator, a plurality of simplex transmitting channels, a corresponding plurality of thermionic vacuum 1 nonconduotive'triode. a commoncathode resistance for said .rstand second triodes, the grid of.said second vtriode being connected to a xed source of positive potential,` and a multivibrator 40 condenserconnected from 'theplate of said second Vtriode to the grid of said Vfirst triode, said negativel lpulseamplitude-modulation signal making said rst triode less conductive, and -said second triode conductive, whereby said multivibrator condenser renders said first triode completely nonconductive, and said second triode fully conductive for a period of time proportional to the amplitude of said pulse-amplitude-modulation signal; whereby the signal appearing in the plate of said second triode is a negative pulse-widthmodulated signal.

3. A multiplex transmitter, comprising a synchronizing pulse generator, a plurality of simplex channels for supplying amplitude modulated signais, a delay line connected to said generator for nels, an electronic switch for each channel connected to said respective delay line sections for actuation thereby, a plurality of means, each including a pulse-width-to-pulse-time modulation converter, respectively connected to receive the o5 output of alternate channels, said switches forming operative links between said channels and the corresponding converter, circuit means for mixing the output of said converters and of said synchronizing generator, and means for transmitting the mixed signals from said mixing circuit means.

4. A transmitter according to claim 3, wherein said delay line comprises a phase corrected delay line having a phase correcting component, and further including means comprising a feedback from a point on said delay line to said generator 19 -fopeont'rhl'ing-.theglse .recurrence rate o'ffs'alid .pulse -.genero.toi:, A

-5. --A-multiplex transmitter oompris'in'g a synchronizingpulse 'generalton aplurlityoflsmplex munies 20 iiitpit i'cuits *for asmanygrou'p's 'of tubes, the tubes'o'f a' group'ha'ving connections to said line lwliich'a're separated by'the. connections of vtubes of other zroups; "whereby 'simplex signals -appear hannels'forfsupply'ing amlitu'demodletedsig- 5 in said' 'outputs successively and in repetitive mals; adelaylinefonneeted tqsaid generatorior deriving@ series of successive .keying pulsesot'rom eachof. the fpulsesLtromsgtid generator, saiilline -having i. a.- -p1ural1ty o'f.=de1a,ying. sections confesponding-.n--numberftothalt'f saidsimrilexh'an- 10 nelsban 'electzzonieswith `for eajohizhannl con- `nectechto sidfrespective dlay line-sectionsfor actuation-thereby, i-.plurality of xcrcuits eaeh of whieh-includes apulse-ampltude-to-plse-wth order1'-and a' mixer circuit to combine the outputs 'of s'fd converter and Isaid output circuits.

MARCEL J. E. GOLAY.

REFERENCES CITED 1 'The'fllow'lng references aye of rec'or'd in Athe le ofthis patent:

UNITED STATES PATENTS -othercontrol lectrodeofsid tube-having e. .con- .nection to?. point @fwd-line. said lnetand 'saidA tubes acting-asa multiplex transmitting distibu` "40 tor linter-cormectingv-said simplex. hannels with said-mu1tiplex-transmitten a.,p1ura.1ity`of.`common THER REFERENCES .Pulse Time ModulatedMu1tip1exRadio Relay System, Electrical Communications, vol. 23. ,pages `159-178, .1946. 

